- ID:
- ivo://CDS.VizieR/J/ApJ/869/145
- Title:
- A 3D Voronoi+Gapper galaxy cluster finder. II.
- Short Name:
- J/ApJ/869/145
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We identify 1901 galaxy clusters (N_g_>=2) with the gapping-filtering in radial velocity (VoML+G) algorithm (Paper I; Campusano+ 2017ApJ...838..109P) on the two-Degree Field Galaxy Redshift Survey (2dFGRS). We present the 341 clusters with at least 10 galaxies that are within 0.009<z<0.14 (the Catalog), of which 254 (~75%) have counterparts in the literature (NED), with the remainder (87) plausibly "new" because of incompleteness of previous searches or unusual galaxy contents. The 207 clusters within z=0.04--0.09 are used to study the properties of the galaxy systems in the nearby universe, including their galaxy contents parameterized by the late-type galaxy fractions (f_L_). For this nearly complete cluster subsample, we find the following: (i) 63% are dominated by early-type galaxies (i.e., the late-type-poor clusters, f_L_<0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M_{sun}_) of 22+/-1 and 12.91+/-0.04, respectively; and (ii) 37% are dominated by late-type galaxies (i.e., the late-type-rich clusters, f_L_>=0.5) with corresponding mean multiplicity and logarithmic virial mass (in units of M_{sun}_) of 15.7+/-0.9 and 12.66+/-0.07, respectively. The statistical analysis of the late-type fraction distribution supports, with a 3{sigma} confidence level, the presence of two population components. It is suggested that the late-type-poor galaxy systems reflect and extend the class of Abell-APM-EDCC clusters and that the late-type-rich systems (~one-third of the total) belong to a new, previously unappreciated class. The late-type-rich clusters, on average high mass-to-light ratio systems, appear to be more clustered on large scales than the late-type-poor clusters. A class of late-type-rich clusters is not predicted by current theory.
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Search Results
- ID:
- ivo://CDS.VizieR/J/ApJ/728/38
- Title:
- AEGIS: demographics of X-ray and optical AGN
- Short Name:
- J/ApJ/728/38
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We develop a new diagnostic method to classify galaxies into active galactic nucleus (AGN) hosts, star-forming galaxies, and absorption-dominated galaxies by combining the [OIII]/H{beta} ratio with rest-frame U-B color. This can be used to robustly select AGNs in galaxy samples at intermediate redshifts (z<1). We compare the result of this optical AGN selection with X-ray selection using a sample of 3150 galaxies with 0.3<z<0.8 and I_AB_<22, selected from the DEEP2 Galaxy Redshift Survey and the All-wavelength Extended Groth Strip International Survey. Among the 146 X-ray sources in this sample, 58% are classified optically as emission-line AGNs, the rest as star-forming galaxies or absorption-dominated galaxies. The latter are also known as "X-ray bright, optically normal galaxies" (XBONGs).
- ID:
- ivo://CDS.VizieR/J/ApJS/220/10
- Title:
- AEGIS-X Deep survey of EGS (AEGIS-XD)
- Short Name:
- J/ApJS/220/10
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present the results of deep Chandra imaging of the central region of the Extended Groth Strip, the AEGIS-X Deep (AEGIS-XD) survey. When combined with previous Chandra observations of a wider area of the strip, AEGIS-X Wide (AEGIS-XW), these provide data to a nominal exposure depth of 800ks in the three central ACIS-I fields, a region of approximately 0.29deg^2^. This is currently the third deepest X-ray survey in existence; a factor ~2-3 shallower than the Chandra Deep Fields (CDFs), but over an area ~3 times greater than each CDF. We present a catalog of 937 point sources detected in the deep Chandra observations, along with identifications of our X-ray sources from deep ground-based, Spitzer, GALEX, and Hubble Space Telescope imaging. Using a likelihood ratio analysis, we associate multiband counterparts for 929/937 of our X-ray sources, with an estimated 95% reliability, making the identification completeness approximately 94% in a statistical sense. Reliable spectroscopic redshifts for 353 of our X-ray sources are available predominantly from Keck (DEEP2/3) and MMT Hectospec, so the current spectroscopic completeness is ~38%. For the remainder of the X-ray sources, we compute photometric redshifts based on multiband photometry in up to 35 bands from the UV to mid-IR. Particular attention is given to the fact that the vast majority the X-ray sources are active galactic nuclei and require hybrid templates. Our photometric redshifts have mean accuracy of {sigma}=0.04 and an outlier fraction of approximately 5%, reaching {sigma}=0.03 with less than 4% outliers in the area covered by CANDELS.
- ID:
- ivo://CDS.VizieR/J/AJ/125/2393
- Title:
- A2256 galaxies redshifts and 1.4GHz fluxes
- Short Name:
- J/AJ/125/2393
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating observed properties across a range of wavelengths. Long believed to represent a cluster merger, recent X-ray and optical results have suggested that in addition to the primary cluster and subcluster there is evidence for a third, poorer system. We present wide-field high-sensitivity 1.4GHz VLA radio observations of Abell 2256 in conjunction with optical imaging and additional spectroscopy. Over 40 cluster radio galaxies are identified, with optical spectroscopy indicating the emission source (star formation or active galactic nucleus) for most of them. While the overall fraction of galaxies exhibiting radio emission is consistent with a large sample of other nearby clusters, we find an increase in the activity level of galaxies belonging to the third system (hereafter "the Group"). Specifically, the Group has relatively more star formation than both the primary cluster and main subcluster. The position of the Group is also coincident with the observed cluster radio relic. We suggest that the Group recently (0.3Gyr) merged with the primary cluster and that this merger, not the ongoing merger of the primary and the main subcluster, might be responsible for many of the unusual radio properties of Abell 2256. Furthermore, the greater star formation activity of the Group suggests that the infall of groups is an important driver of galaxy evolution in clusters.
- ID:
- ivo://CDS.VizieR/J/ApJS/200/8
- Title:
- AGES: the AGN and Galaxy Evolution Survey
- Short Name:
- J/ApJS/200/8
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- The AGN and Galaxy Evolution Survey (AGES) is a redshift survey covering, in its standard fields, 7.7deg^2^ of the Bootes field of the NOAO Deep Wide-Field Survey. The final sample consists of 23745 redshifts. There are well-defined galaxy samples in 10 bands (the B_W_, R, I, J, K, IRAC 3.6, 4.5, 5.8, and 8.0um, and MIPS 24um bands) to a limiting magnitude of I<20mag for spectroscopy. For these galaxies, we obtained 18163 redshifts from a sample of 35200 galaxies, where random sparse sampling was used to define statistically complete sub-samples in all 10 photometric bands. The median galaxy redshift is 0.31, and 90% of the redshifts are in the range 0.085<z<0.66. Active galactic nuclei (AGNs) were selected as radio, X-ray, IRAC mid-IR, and MIPS 24um sources to fainter limiting magnitudes (I<22.5mag for point sources). Redshifts were obtained for 4764 quasars and galaxies with AGN signatures, with 2926, 1718, 605, 119, and 13 above redshifts of 0.5, 1, 2, 3, and 4, respectively. We detail all the AGES selection procedures and present the complete spectroscopic redshift catalogs and spectral energy distribution decompositions. Photometric redshift estimates are provided for all sources in the AGES samples.
- ID:
- ivo://CDS.VizieR/J/ApJ/751/52
- Title:
- AGN candidates from the WISE, 2MASS, RASS (W2R)
- Short Name:
- J/ApJ/751/52
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We have developed the "S_IX_" statistic to identify bright, highly likely active galactic nucleus (AGN) candidates solely on the basis of Wide-field Infrared Survey Explorer (WISE), Two Micron All-Sky Survey (2MASS), and ROSAT all-sky survey (RASS) data. This statistic was optimized with data from the preliminary WISE survey and the Sloan Digital Sky Survey, and tested with Lick 3m Kast spectroscopy. We find that sources with S_IX_<0 have a >~95% likelihood of being an AGN (defined in this paper as a Seyfert 1, quasar, or blazar). This statistic was then applied to the full WISE/2MASS/RASS dataset, including the final WISE data release, to yield the "W2R" sample of 4316 sources with S_IX_<0. Only 2209 of these sources are currently in the Veron-Cetty and Veron (VCV) catalog of spectroscopically confirmed AGNs, indicating that the W2R sample contains nearly 2000 new, relatively bright (J<~16) AGNs. We utilize the W2R sample to quantify biases and incompleteness in the VCV catalog. We find that it is highly complete for bright (J<14), northern AGNs, but the completeness drops below 50% for fainter, southern samples and for sources near the Galactic plane. This approach also led to the spectroscopic identification of 10 new AGNs in the Kepler field, more than doubling the number of AGNs being monitored by Kepler. The W2R sample contains better than 1 bright AGN every 10 deg^2^, permitting construction of AGN samples in any sufficiently large region of sky.
- ID:
- ivo://CDS.VizieR/J/ApJS/172/383
- Title:
- AGN candidates in the COSMOS field
- Short Name:
- J/ApJS/172/383
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present spectroscopic redshifts for the first 466 X-ray and radio-selected AGN targets in the 2deg^2^ COSMOS field. Spectra were obtained with the IMACS instrument on the Magellan (Baade) telescope, using the nod-and-shuffle technique. We identify a variety of type 1 and type 2 AGNs, as well as red galaxies with no emission lines. Our redshift yield is 72% down to i_AB_=24, although the yield is >90% for i_AB_<22. We expect the completeness to increase as the survey continues. When our survey is complete and additional redshifts from the zCOSMOS project are included, we anticipate ~1100 AGNs with redshifts over the entire COSMOS field. Our redshift survey is consistent with an obscured AGN population that peaks at z~0.7, although further work is necessary to disentangle the selection effects.
- ID:
- ivo://CDS.VizieR/J/ApJ/613/682
- Title:
- AGN central masses and broad-line region sizes
- Short Name:
- J/ApJ/613/682
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple line measurements, we find that the highest precision measure of the virial product c{tau}{Delta}V^2^/G, where {tau} is the emission-line lag relative to continuum variations and {Delta}V is the emission-line width, is obtained by using the cross-correlation function centroid (as opposed to the cross-correlation function peak) for the time delay and the line dispersion (as opposed to FWHM) for the line width and by measuring the line width in the variable part of the spectrum.
- ID:
- ivo://CDS.VizieR/J/A+A/590/A68
- Title:
- AGN data and absorption-line measurements
- Short Name:
- J/A+A/590/A68
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- Doubly ionized silicon (SiIII) is a powerful tracer of diffuse ionized gas inside and outside of galaxies.It can be observed in the local Universe in ultraviolet (UV) absorption against bright extragalactic background sources. We here present an extensive study of intervening SiIII-selected absorbers and study the properties of the warm circumgalactic medium (CGM) around low-redshift (z<0.1) galaxies. We analyzed the UV absorption spectra of 303 extragalactic background sources, as obtained with the Cosmic Origins Spectrograph (COS) on-board the Hubble Space Telescope (HST). We developed a geometrical model for the absorption-cross section of the CGM around the local galaxy population and compared the observed SiIII absorption statistics with predictions provided by the model. We also compared redshifts and positions of the absorbers with those of ~64,000 galaxies using archival galaxy-survey data to investigate the relation between intervening SiIII absorbers and the CGM. Along a total redshift path of {Delta}z~24, we identify 69 intervening SiIII systems that all show associated absorption from other low and high ions (e.g., HI, SiII, SiIV, CII, CIV). We derive a bias-corrected number density of dN/dz(SiIII)=2.5+/-0.4 for absorbers with column densities log N(SiIII)>12.2, which is ~3 times the number density of strong MgII systems at z=0. This number density matches the expected cross section of a SiIII absorbing CGM around the local galaxy population with a mean covering fraction of <f_c_>=0.69. For the majority (~60 percent) of the absorbers, we identify possible host galaxies within 300km/s of the absorbers and derive impact parameters {rho}<200kpc, demonstrating that the spatial distributions of SiIII absorbers and galaxies are highly correlated. Our study indicates that the majority of SiIII-selected absorbers in our sample trace the CGM of nearby galaxies within their virial radii at a typical covering fraction of ~70 percent. We estimate that diffuse gas in the CGM around galaxies, as traced by SiIII contains substantially more (more than twice as much) baryonic mass than their neutral interstellar medium.
- ID:
- ivo://CDS.VizieR/J/ApJS/143/257
- Title:
- AGN emission line properties
- Short Name:
- J/ApJS/143/257
- Date:
- 21 Oct 2021
- Publisher:
- CDS
- Description:
- We present measurements of the UV/optical emission line parameters in a sample of 158 active galactic nuclei observed with the Faint Object Spectrograph on the Hubble Space Telescope (HST), prior to the installation of COSTAR. We use an automated technique that accounts for galactic reddening, includes iron emission blends, galactic and intrinsic absorption lines, and performs multicomponent fits to the emission line profiles. We present measured line parameters (equivalent width and FWHM) for a large number (28) of different UV/optical lines, including upper limits for undetected lines.